Investigation of Magnetostrictive Comb Transducers for Guided Wave Pipe Inspection

Open Access
Waller, Matthew David
Area of Honors:
Engineering Science
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Joseph Lawrence Rose, Thesis Supervisor
  • Judith A Todd, Honors Advisor
  • Clifford Jesse Lissenden Iii, Faculty Reader
  • Bernhard R Tittmann, Faculty Reader
  • magnetostrictive
  • guided wave
  • nondestructive evaluation
Modern society relies on vast networks of pipelines to transport essential commodities including crude and refined fuels for transportation and heating, chemicals destined for refiners and manufacturers, and agricultural fertilizers. Since many of these substances are potentially hazardous to the environment and humans alike, pipeline integrity is an important concern for safety as well as economic reasons. Pipelines are subjected to various stresses throughout their service lives, the most common of which is corrosion. To protect pipes from corrosion and other damaging effects, pipelines are frequently buried underground or sealed with thick coatings. While these steps are intended to protect the pipe, they make inspections for damage especially difficult. Ultrasonic guided waves (UGW) are a promising solution for pipeline inspection because of the demonstrated capability to inspect long ranges, detect defects hidden underneath coatings, and to reliably characterize defects. Specifically, the use of shear waves excited and received by magnetostrictive transducers has shown promise for in-service inspection. To investigate magnetostrictive comb transducers for guided wave pipe inspection, a prototype of a new inspection system available at FBS, Inc. was obtained. The goal of the research was to optimize various instrumentation, actuator, and receiver parameters to see what kinds of inspection problems may be studied with this system. In this thesis, sources of pipeline damage are reviewed, basic elastic guided wave theory is introduced, and magnetostrictive transducer technology is described. A computational model of guided wave propagation is studied and a sample problem is presented. Ribbon cables and MsS circuits of various shapes and apertures were used to excite and measure the SH0 guided wave mode via the pulse-echo technique in several pipes including a control pipe with targets, a pipe with simulated corrosion, a pipe with real pitting corrosion, and a pipe with a viscoelastic coating. The experimental results are presented and used to compare the different ribbon cables, MsS circuits, and apertures based on performance in detecting and resolving defects for different inspection problems. Raw data is presented, as well as signal amplitude comparisons created using MATLAB.